Metabolic Bone Diseases — MCQs
A child presents with poor growth and swelling at joints. A radiograph of his wrist is given below. Lab investigations reveal serum ALP levels of >1500. What is the possible diagnosis?
All are features of Paget's disease except which of the following?
Following are features of Paget's disease except -
Which of the following clinical findings is characteristic of both osteomalacia and rickets?
Primary hyperparathyroidism is suggested by all of the following, except which of the following?
Which of the following is true about osteoporosis?
What does the fallen fragment sign indicate in radiology?
What type of lesions in the skull bones can be identified on this X-ray?
In which condition is the 'Picture frame vertebra' seen?
Spine MRI shows 'pencil-sharpened' vertebral bodies and 'H-shaped' vertebrae on T1-weighted images. Most likely diagnosis?
Metabolic Bone Diseases Indian Medical PG Practice Questions and MCQs
Question 1: A child presents with poor growth and swelling at joints. A radiograph of his wrist is given below. Lab investigations reveal serum ALP levels of >1500. What is the possible diagnosis?
- A. Rickets (Correct Answer)
- B. Osteoporosis
- C. Osteomalacia
- D. Osteogenesis imperfecta
Explanation: ***Rickets*** - The combination of **poor growth**, **joint swelling**, and **elevated alkaline phosphatase (ALP)** in a child strongly indicates rickets, a condition of defective bone mineralization in growing bones. - The radiograph of the wrist would likely show typical findings like **widened growth plates**, **fraying** and **cupping of metaphyses**, and **decreased bone density**, which are characteristic of rickets. *Osteoporosis* - This condition is characterized by **reduced bone mass** and **fragile bones**, typically seen in older adults or due to secondary causes, and is not primarily linked to joint swelling in children. - While ALP levels can be normal or slightly elevated in osteoporosis, a level of >1500 is highly suggestive of active bone formation or breakdown, not typically seen in osteoporosis. *Osteomalacia* - This is defective bone mineralization in adults after growth plates have fused, leading to **bone softening** and **pain**, typically not presenting with joint swelling as a primary symptom. - While it also involves high ALP and bone demineralization, the clinical context of a *child* with growth issues points more specifically to rickets. *Osteogenesis imperfecta* - This is a group of **genetic disorders** characterized by **brittle bones** that fracture easily, often accompanied by **blue sclerae** and **hearing loss**, which are not mentioned in the presentation. - While bone fragility is present, it does not typically cause the described joint swelling or the significantly elevated ALP levels seen in this case.
Question 2: All are features of Paget's disease except which of the following?
- A. Defect in osteoclasts
- B. Affects only axial skeleton (Correct Answer)
- C. Can lead to hearing loss
- D. Can lead to bone cancer
Explanation: ***Affects only axial skeleton*** - This statement is **FALSE** and therefore the correct answer to this "EXCEPT" question. - Paget's disease **can affect any bone in the body**, including both axial skeleton (spine, skull, pelvis) and appendicular skeleton (femur, tibia, humerus) [1]. - Common sites include: **pelvis (70%), spine, skull, femur, and tibia** [1]. - While it frequently affects axial bones, it is **not exclusive** to them. *Defect in osteoclasts* - This is a TRUE feature of Paget's disease. - The disease is characterized by **abnormal, hyperactive osteoclasts** with increased number of nuclei (up to 100 vs normal 3-5). - These osteoclasts show **excessive bone resorption activity** followed by disorganized bone formation [1]. - The primary defect involves **increased osteoclast activity and sensitivity to RANKL**. *Can lead to hearing loss* - This is a TRUE feature of Paget's disease. - Skull involvement can lead to **compression of cranial nerve VIII** (vestibulocochlear nerve) [1]. - Enlargement and disorganization of temporal bone can cause **conductive or sensorineural hearing loss**. - Occurs in approximately 30-50% of patients with skull involvement. *Can lead to bone cancer* - This is a TRUE feature of Paget's disease. - **Osteosarcoma** develops in approximately **1%** of Paget's disease patients. - Risk is higher in patients with **polyostotic disease** and long-standing involvement. - This is a rare but serious complication with poor prognosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1192-1194.
Question 3: Following are features of Paget's disease except -
- A. Increased Urinary excretion of hydroxyproline
- B. Deformity of bones
- C. Lowered serum alkaline phosphatase (Correct Answer)
- D. Secondary osteosarcoma
Explanation: ***Lowered serum alkaline phosphatase*** - Paget's disease is characterized by markedly **increased bone turnover**, involving both excessive bone resorption and disorganized bone formation. - This high bone formation activity leads to a significant **elevation in serum alkaline phosphatase (ALP)**, not a lowering, making this the incorrect feature [1]. *Increased Urinary excretion of hydroxyproline* - **Hydroxyproline** is a major component of **collagen**, and its urinary excretion is a marker of **collagen degradation** and bone resorption. - In Paget's disease, there is rapid and chaotic bone remodeling, leading to increased breakdown of collagen and thus **elevated urinary hydroxyproline**. *Deformity of bones* - The disorganized and rapid bone remodeling in Paget's disease results in structurally unsound and **enlarged, weakened bones**. - This often leads to **bone deformities**, bowing of long bones, and an increased risk of fractures due to the abnormal bone architecture [1], [2]. *Secondary osteosarcoma* - Paget's disease is a significant risk factor for the development of **secondary osteosarcoma**, a rare but aggressive bone cancer. - While most cases of Paget's disease do not progress to malignancy, the chronic and intense bone remodeling activity can predispose to malignant transformation, particularly in areas of long-standing disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1191-1194. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 660-661.
Question 4: Which of the following clinical findings is characteristic of both osteomalacia and rickets?
- A. frontal bossing in the skull
- B. defects in tooth enamel
- C. muscle weakness (Correct Answer)
- D. prominent costochondral junctions
Explanation: ***Muscle weakness*** - **Muscle weakness** is a common symptom in both rickets (in children) and osteomalacia (in adults) due to **impaired mineralization of bone matrix** and compromised muscle function [1]. - This weakness often presents as **difficulty walking**, standing, or performing daily activities. *Frontal bossing in the skull* - **Frontal bossing** (prominent forehead) is a specific sign of **rickets** in children, resulting from excessive unmineralized osteoid on the skull [1]. - It is not typically seen in adult **osteomalacia**, as the skull bones are already formed. *Defects in tooth enamel* - **Defects in tooth enamel** are primarily associated with a prolonged and severe deficiency of **vitamin D or calcium during tooth development**, which is characteristic of childhood **rickets**. - While vitamin D and calcium are crucial for overall bone health, enamel defects are less common or severe in adult-onset **osteomalacia**. *Prominent costochondral junctions* - **Prominent costochondral junctions** (rachitic rosary) are a classic sign of **rickets** in children, caused by the enlargement of the cartilage at the ends of the ribs due to defective mineralization [1]. - This finding is specific to growing children and is not observed in adults with **osteomalacia**.
Question 5: Primary hyperparathyroidism is suggested by all of the following, except which of the following?
- A. Increased serum calcium
- B. Low urinary calcium levels (Correct Answer)
- C. Increased urinary calcium
- D. Decreased PTH levels
Explanation: ***Low urinary calcium*** - In primary hyperparathyroidism, **urinary calcium levels are typically elevated** due to increased calcium reabsorption in the kidneys [2]. - **Low urinary calcium levels** would suggest a different condition, such as **hypoparathyroidism** or a renal issue affecting calcium excretion [5]. *Increased PTH* - Primary hyperparathyroidism is characterized by **elevated parathyroid hormone (PTH)** levels, as the parathyroid glands are overactive [1][3]. - High PTH contributes to increased serum calcium and bone resorption [2]. *Increased serum calcium* - A hallmark of primary hyperparathyroidism is **hypercalcemia**, resulting from increased bone resorption and renal tubular reabsorption of calcium [1][2]. - The condition often leads to symptoms such as **kidney stones** and **bone pain** due to elevated serum calcium levels [3][4]. *Increased C-AMP* - Elevated levels of **cyclic AMP (C-AMP)** in urine are observed in primary hyperparathyroidism due to the stimulatory effect of PTH on renal tubular reabsorption of calcium. - Increased C-AMP correlates with the action of PTH in promoting calcium release from the bones [2].
Question 6: Which of the following is true about osteoporosis?
- A. Raised alkaline phosphatase
- B. Cod fish vertebrae (Correct Answer)
- C. Low calcium
- D. Low phosphate
Explanation: **Cod fish vertebrae** - **Cod fish vertebrae** (or biconcave vertebral bodies) are a characteristic radiological sign seen in **osteoporosis**, resulting from weakened vertebral bodies bulging under pressure from disc material. - This appearance is due to the softening of the vertebral endplates, allowing the intervertebral discs to indent the adjacent vertebral bodies. - This is a classic finding in severe osteoporosis on lateral spine radiographs. *Raised alkaline phosphatase* - **Alkaline phosphatase (ALP)** levels are typically **normal in osteoporosis** because bone turnover, while unbalanced, does not involve a significant increase in osteoblastic activity that would elevate ALP. - **Elevated ALP** is more characteristic of conditions with increased osteoblastic activity, such as **Paget's disease of bone**, **osteomalacia**, or bone metastases. *Low calcium* - **Serum calcium levels** are typically **normal in osteoporosis** as the body maintains calcium homeostasis through hormonal regulation, even if bone density is low. - **Low calcium (hypocalcemia)** is more commonly associated with conditions like **hypoparathyroidism** or severe **vitamin D deficiency** leading to **osteomalacia**. *Low phosphate* - **Serum phosphate levels** are typically **normal in osteoporosis**, similar to calcium, due to tightly regulated homeostatic mechanisms. - **Low phosphate (hypophosphatemia)** can be seen in conditions like **osteomalacia** (especially those related to vitamin D deficiency or renal phosphate wasting) but not typically in osteoporosis.
Question 7: What does the fallen fragment sign indicate in radiology?
- A. Indicates a simple bone cyst (Correct Answer)
- B. Indicates osteosarcoma
- C. Indicates an aneurysmal bone cyst
- D. Indicates adamantinoma
Explanation: ***Indicates a simple bone cyst*** - The **fallen fragment sign** is a classic radiographic finding seen in **simple bone cysts** (unicameral bone cysts), particularly after a pathological fracture. - It occurs when a **fractured piece of bone** falls through the fluid-filled cyst cavity due to gravity, creating a characteristic appearance that indicates a benign, fluid-filled lesion. - This sign is considered **pathognomonic** for simple bone cysts. *Indicates osteosarcoma* - Osteosarcoma is a **malignant bone tumor** characterized by aggressive bone destruction and **osteoid formation**. - It typically does not demonstrate a fallen fragment sign; instead, it often shows a **Codman triangle** or **sunburst periosteal reaction**. - The aggressive nature and solid tumor composition make this sign incompatible with osteosarcoma. *Indicates an aneurysmal bone cyst* - An aneurysmal bone cyst (ABC) is a **benign, vascular bone lesion** that is usually multiloculated and blood-filled. - While it can cause bone expansion and pathological fractures, the fallen fragment sign is **not characteristic** of ABCs, which are typically hemorrhagic and contain blood-filled septa rather than clear fluid. - ABCs show a characteristic **fluid-fluid level** on imaging, not a fallen fragment. *Indicates adamantinoma* - Adamantinoma is a **rare, low-grade malignant bone tumor** most commonly found in the tibia. - This tumor does not exhibit a fallen fragment sign; its radiographic features often include **lobulated osteolytic lesions** with a sclerotic rim. - It is a solid tumor without the fluid-filled cavity necessary for this sign.
Question 8: What type of lesions in the skull bones can be identified on this X-ray?
- A. Paget's disease (Correct Answer)
- B. Multiple myeloma
- C. Osteosarcoma
- D. Osteomyelitis
Explanation: ***Paget's disease*** - An X-ray of the skull in Paget's disease typically shows **thickening of the skull vault** and areas of both **osteolysis** and **osteosclerosis**, leading to a characteristic "cotton wool" appearance. - The disease involves abnormal bone remodeling, leading to enlarged and weakened bones susceptible to deformity and fracture. *Multiple myeloma* - On a skull X-ray, multiple myeloma usually presents as multiple, sharply-defined, **"punched-out" lytic lesions** without a sclerotic border. - These lesions reflect areas where malignant plasma cells have destroyed bone, which is distinct from the mixed lytic and sclerotic changes of Paget's disease. *Osteosarcoma* - Osteosarcoma is a **primary bone malignancy** that typically presents as a solitary lesion with a mixture of lytic and sclerotic areas, often with a **sunburst or Codman's triangle** periosteal reaction. - It most commonly affects long bones in younger individuals and is a much less common presentation in the skull compared to other bone conditions. *Osteomyelitis* - Osteomyelitis is an **infection of the bone** that would appear on an X-ray as areas of bone destruction (lysis) and new bone formation (sclerosis), often with **sequestrum** (dead bone) and **involucrum** (new bone formation around the infection). - While it can affect the skull, its imaging features would typically be localized signs of infection rather than the widespread, generalized changes seen in Paget's disease.
Question 9: In which condition is the 'Picture frame vertebra' seen?
- A. Paget disease (Correct Answer)
- B. Osteopetrosis (marble bone disease)
- C. Ankylosing spondylitis (AS)
- D. Osteoporosis
Explanation: ***Paget disease*** - The "picture frame vertebra" sign is a classic radiographic finding in **Paget disease**, characterized by **cortical thickening** and sclerosis around the vertebral body circumference, resembling a picture frame. - This appearance is due to the disordered bone remodeling processes (increased osteoclastic bone resorption followed by disorganized osteoblastic new bone formation) characteristic of Paget disease. *Osteopetrosis (marble bone disease)* - Osteopetrosis is characterized by **increased bone density** due to defective osteoclast function, leading to bones that are dense but brittle. - It does not typically present with the specific "picture frame" appearance of individual vertebrae, but rather with diffuse sclerosis of bones. *Ankylosing spondylitis (AS)* - Ankylosing spondylitis primarily affects the **axial skeleton**, causing inflammation and eventual fusion of the vertebrae (leading to a "bamboo spine" appearance). - While it involves the spine, it does not produce the "picture frame" vertebral sign seen in Paget disease. *Osteoporosis* - Osteoporosis is characterized by **reduced bone mass** and microstructural deterioration of bone tissue, leading to increased bone fragility and fracture risk. - Radiographically, it shows **decreased bone density** and possible vertebral compression fractures, which is the opposite of the increased bone density and cortical thickening seen in the "picture frame" sign.
Question 10: Spine MRI shows 'pencil-sharpened' vertebral bodies and 'H-shaped' vertebrae on T1-weighted images. Most likely diagnosis?
- A. Sickle cell disease (Correct Answer)
- B. Paget's disease
- C. Thalassemia
- D. Osteopetrosis
Explanation: ***Sickle cell disease*** - **'Pencil-sharpened' vertebral bodies** and **'H-shaped' vertebrae** are characteristic findings in sickle cell disease due to chronic **ischemic necrosis** of the vertebral endplates. - This vertebral deformity arises from the collapse of the central portion of the vertebral body, often associated with episodes of **vaso-occlusion**. *Paget's disease* - Characterized by abnormal bone remodeling, leading to **bone enlargement** and thickening, not vertebral notching or collapse. - Common radiological findings include **cotton wool appearance** of the skull and **sclerosis** of the vertebrae, distinct from the described MRI findings. *Thalassemia* - Causes significant **bone marrow expansion** due to ineffective erythropoiesis, leading to cortical thinning and widened medullary spaces. - While it can affect bone morphology, it typically does not produce the specific 'H-shaped' or 'pencil-sharpened' vertebral body deformities. *Osteopetrosis* - Known as **'marble bone disease'**, characterized by abnormally dense bones due to defective osteoclast function. - Radiologically, it presents with **generalized increased bone density** and obliterated marrow spaces, which is opposite to the changes seen in sickle cell disease.
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